Superconducting wires have been widely used for example in NMR (Nuclear Magnetic Resonance) devices and MRI (Magnetic Resonance Imaging) devices. In recent years, rare earth-based high temperature superconducting wires (REBCO wires) have been put into production, and research and development using these wires have been ongoing.
In a coil made of a superconducting wire, a superconducting layer must have a filamentary structure in order to reduce a screening current-induced magnetic field or AC loss. However, orientation must be in a uniform direction in crystal growth in order to produce a REBCO wire having high critical current, and therefore, a single-filamentary tape wire having a width of several mm and a thickness of several hundred μm is typically produced, rather than a multi-filamentary wire having a circular cross section as in the case of a NbTi wire. As a solution to the problem, a scribing wire produced by forming a number of lengthwise grooves on a wire substrate and forming a superconducting layer into multiple filaments has been suggested, and mechanical grinding, chemical etching, and cutting by laser irradiation, etc., have been suggested as scribing methods (PTL 1).